In one aspect, this invention relates to the design of a cast on pipe anode. In another aspect, the invention relates to a pipeline havig anodes thereon. In another aspect, the invention relates to a method for laying a pipeline. In other aspects, the invention relates to methods for providing a pipe with cast one anodes.
Sacrificial anodes are commonly used to cathodically protect steel structures, for example, steel pipelines. One type of anode used on pipelines is cast directly onto the pipe sections before the sections are connected to form the pipeline.
Pre-cast on anodes are in use on pipelines that are installed by a dragging or towing operations. However, pre-cast on anodes are not used on pipelines that are installed by reel barge methods. In such operations, the pipelines are stored on large reels and it is believed that cast on anodes of previously known designs would become damaged by cracking and spalling to too great an extent during the coiling and uncoiling operations to provide adequate protection. The problem of cracking and spalling would be exacerbated due to the brittleness of known suitable anode materials. This brittleness cannot be alleviated by alloy changes or the addition of other elements because anode alloys must meet strict specifications as to chemical composition in order to be effective. Most alloys and elements that would promote ductility would be cathodic to the anode material and would thereby significantly reduce current efficiency and the effectiveness of the anode.
Offshore, pipelining operations involve the use of reel barges. The pipeline is unreeled during the laying operation of the pipeline. The bottleneck for the operation is the installation of the anodes on the pipeline. Each anode delays laying progress for in the range of from about 20 to 45 minutes. Successful cast on anodes which could be used on a reel barge could revolutionize pipeline laying methods. The development of such anodes would make a semicontinuous operation a fully continuous one and result in great time and labor savings.